Fluid pressure control



Aug. 13, 1940. R. TYLER FLUID PRESSURE CONTROL Filed Sept. 26, 1938 J 65a4 4 9 6 4 4 5 2 65 Q9 1 59 Reduction Gear Electric Motor R Tm mY E M 2g y F 4 D l S 3 3 M 6 2 5 H 3 Patented Aug." 13, 1940 UNITED STATESFLUID PRESSURE CONTROL Ransom Tyler, Greenfield, we, assignor to TheOilgear Company, Milwaukee, Wis., a corporation of Wisconsin ApplicationSeptember 2c, 1938, Serial No. 231.688

13Claims.

This invention relates to apparatus for controlling the pressure in afluid circuit, and it is particularly adapted for controlling thepressure of the liquid employed to operate hydraulic presses and thelike.

An object of the invention is to provide a control by means of which thepressure in a fluid circuit may be gradually varied through apredtetermined range during a predetermined period 0 ime.

Another object is to provide a control by means during each cycle ofoperation of the control and which will have the working parts thereofin position to start another cycle at the completion ofeach cycle. g

Another object is to provide a control for gradually varying thepressure in a fluid circuit through a predetermined range first at onerate and then at a different rate.

Another object is to provide a control of the above described characterwhich is positive and precise in operation. v

Other objects and advantages will appear from the descriptionhereinafter given 01' a control in which the invention is embodied.

The invention is exemplified by the control shown schematically inaccompanying drawing in which theviews are as follows:

Fig. 1 is a diagrammatic view showing a hydraulic press. provided with acontrol in which the invention is embodied.

Fig. 2 is a view showing a selector valve in a.

position diflerent' from that shown in Fig. 1.

Figs. 3 and4 are views showing a reversing valve in positions difierentfrom that shown in Fig. 1.

For the purpose of illustration, a control embodying the invention hasbeen shown applied to a. hydraulic press which is employed to compressmaterial having a high liquid content but the invention is not limitedto such use. a

Since the press per se forms no part of thewhich energizes motor 4-5andwhich draws" liquid from a reservoir I and discharges it into asupply channel 9, and a reversing valve III which is arranged in a valvecasing II and controls the flow of liquid to and from motor 4-5.

Reversing valve i0 has two spaced apart heads or pistons formed thereonand closely fitted in 6 the bore i2 of casing ii. Bore l2has threeannular grooves or ports l4, l5, and it formed in its side wall and itsupper end is connected by a channel I! to a channel l8 whichcommunicates with the lower end oi bore l2 and dis- 10 charges intoreservoir 8.

Port i4 is arranged between the other two ports and has supply channel 9connected thereto. Port i5 is controlled by and is narrower than thelower piston on valve ill and is con-- nected by a channel l9 to thelower end of cylinder 4. Port I6 is controlled by and is wider than theupper piston on valve ill and is connected by channel to the upper endof cylinder 4. I 20 When valve Ill is in the position shown in Fig.

1, the wide lower piston on valve l0 blocks port i5 so that piston 5 anddie 3 are supported by the liquid trapped in the lower end of cylinder4, and the narrow upper piston on valve III is positioned between theedges of wide port l6 so that the liquid discharged by pump .I may flowthrough channel 9, bore l2 and channels I! and I8 into reservoir 8.

When valve i0 is moved downward to the limit of its movement as showninv Fig. 4, Port 15 is open to port l4 so that liquid from pump I mayflow through channel 9, bore l2 and channel I9 to the lower end ofcylinder 4 and raise piston 5 and die 3, and port i6 is open to channeli1 so that liquid ejected from the upper end of cylinder 4 by piston 5during its upward movement may flow through channel 20, bore l2 andchannels I! and I8 into reservoir 8.

When valve i0 is moved upward to the limit of its movement as shown inFig. 3, port 5 is open to port l4 so that liquid from pump 1 may flowthrough channel 9, bore i2 and channel 20 to the upper end of cylinder 4and movepiston 5 downward, and port i5 is open to channel It so thatliquid ejected from the lower end of cylinder 4 by piston 5 during itsdownward movement may flow through channel l9, bore l2 and channel I. tothe reservoir 8.

It mold I contains a quantity of material from which liquid is to bepressed as the material is compressed by die 3, the pressing forceexerted by die3- should be gradually varied from an initial minimum toanultimatemaximumin order that the liquid content of the material may be7 gradually eliminated and the material pressed into a substantiallysolid cake or slab having certain desired characteristics.

This is accomplished by permitting a part of the liquid discharged bythe pump to escape through a relief valve and by adjusting the valve togradually increase the resistance thereof so that pump pressure isgradually increased with a resultant gradual increase in the pressingforce exerted by die 3 upon the material in mold I.

If but one relief valve were employed, it would be necessary to readjustit after each pressing operation before another pressing operation couldbe started. In order to avoid such a delay andthe necessity of manualadjustment of the relief valve, two relief valves are provided and theresistance of one is decreased while the resistance of the other isbeing increased, and communication is blocked between the pump and therelief valve having the lower resistance during the time that theresistance of the other relief valve is being increased.

As shown, the control is provided with a low pressure relief valve 25and a high pressure relief valve 26 the resistances of which aresimultaneously varied inversely to each other as will presently appear.High pressure relief valve 26 may have its inlet connected directly tosupply channel 9 by a channel 21 but communication between low pressurerelief valve 25 and channel 9 is controlled by a selector valve 28 whichhas two heads or pistons formed thereon and closely fitted in the bore29 of a valve casing 30.

Bore 29 has two annular grooves or ports 3| and 32 formed in its walland both of its ends connected to a drain channel 33 which dischargesinto reservoir 8. Port 3| is connected to supply channel 9 by a channel34, and port 32 is connected to the inlet of relief valve 25 by a channel 35. q

Selector valve 28 may be operated in any suitable manner but it has beenshown as being urged toward the right by a spring 36 arranged in one endof bore 29 and as being adapted to be moved toward the left by asolenoid 31 having its core connected to the stem of valve 28 and itswinding connected to a control panel 38 by conductors arranged in acable 39.

The liquid exhausted from supply channel 9 through relief valve 25 orrelief valve 26 is discharged into reservoir 8 through channels arrangedin any suitable manner. For example, the outlet of low pressure reliefvalve 25 may be connected by a channel 40 to that end of bore 29containing spring 36 so that liquid exhausted through relief valve 25may flow therethrough into drain channel 33, and the outlet of reliefvalve 26 may be connected by a channel 4| to the spring chamber ofrelief valve 25 so that liquid exhausted through relief valve 26 mayflow therethrough and through channel 40 and the left end of bore 29into drain channel 33.

Low pressure relief valve 25 has its valve member 44 urged toward itsseat by a spring 45 the resistance of which may be varied by turning ascrew v46 so as to vary the pressure required to open the valve from apredetermined minimum to a predetermined maximum, and high pressurerelief valve 26 has its valve member 41 urged toward its seat by aspring 48 the resistance of which may be varied by turning a screw 49 soas to vary the pressure required to open the valve from a minimum, whichis approximately equal to the maximum pressure required to open valve25, to a predetermined maximum.

Springs 45 and 48 may be so proportioned that turning screw 46 at auniform speed will cause the pressure required to open valve 25 toincrease at a given rate from a predetermined minimum, for instance 150#per sq. in., to an intermediate value and turning screw 49 at the sameuniform speed will cause the pressure required to open valve 26 to varyat the same rate from the intermediate value to a predetermined maximum,for instance 1800# per sq. in., so that the pressure in channel 9 andconsequently the pressing force exerted by die 3 is varied at a uniformrate through a predetermined range during a predetermined period oftime.

It is often desirable that the pressing force be varied at one rateduring one part of a pressing operation and at a different rate duringanother part of the pressing operation. This may be accomplished by soproportioning springs 45 and 48 that turning screw 46 at a uniform speedwill cause the pressure required to open valve 25 to increase at a onerate from a predetermined minimum for instance 150# per sq. in.,

to an intermediate value, for instance 300# per sq. in., and turningscrew 49 at the same uniform speed will cause the pressure required toopen valve 26 to vary at a different rate from the intermediate value toa predetermined maximum, for instance 1800# per sq. in., so that thepressure in channel 9 and consequently the force exerted by die 3 isuniformly varied at one rate while liquid is being discharged throughone relief valve and at a different rate while liquid is beingdischarged through the other relief valve.

In order that the resistances of valves 25 and 26 may be simultaneouslyvaried inversely to each other, screws 46 and 49 may be rotated inopposite directions and have threads of the same hand, or they may berotated in the same direction and have opposite hand threads.

As shown, screw 46 has a right hand thread and is connected to a shaft53 which has a driven gear 54 splined thereon, screw 49 has a left handthread and is connected to a shaft 55 which has a driven gear 56 splinedthereon, gears 54 and 56 mesh with a driving gear 51 fixed upon a shaft58 which is driven through a speed reducer or a reduction gear 59 by areversible electric motor 60, and all three of these shafts arejournaled in a gear case 6| which encloses the gears and restrains themfrom axial movement.

The arrangement is such that, when motor 69 is energized, gear 51 willrotate gears 54 and 56 at a very slow rate in the same direction andthereby cause one of screws 46 and 49 to gradually advance and increasethe tension of one relief valve spring and the other screw to graduallyretract and decrease the tension of the other relief valve spring. Theresistances of valves 25 and 26 are thus simultaneously varied inverselyto each other at a gradual and uniform rate. The individual resistancesof relief valves 25 and 26 may be initially adjusted by means of acoupling 62, which connects screw 46 to shaft 53, and a coupling 63which connects screw 49 to shaft 55.

Current for energizing motor is supplied thereto through a cable 64 fromcontrol panel 38 to which current is supplied through a cable 65 from asuitable source not shown. Motor 60 is controlled by plurality ofmanually operable push button switches 66, which are arranged in controlpanel 38, and by two, limit switches 61 and 68 which are connected tocontrol panel 38 by cables 59 and respectively.

Switch 61, operation of which causes motor 61! to stop, is arranged insuch a position that it is operated by the end of shaft 53 when screw 46has reduced the resistance of low pressure relief valve 25 to thepredetermined minimum. Switch 68, operation of which causes motor 60 tobe reversed, is arranged in such a position that it is operated by theend of shaft 55 when screw 59 has reduced the resistance of highpressure relief valve 25 to the predetermined minimum at which time theresistance of low pres-- "deenergized so that spring 36 may shift valve28 to the position shown in Fig. 1.

Operation Assuming that the several parts are in the positions shown inFig. 1, that mold 9 contains a quantity of material to be compressed andthat pump '5 is running, the apparatus will function as follows:

Pump i will discharge through channel 3, reversi'ng valve casing ii andchannels H and it into reservoir 8, and piston 5 will be supported bythe liquid trapped in the lower end of cylinder 5.

When reversing valve it is moved upward to the position shown in Fig. 3,liquid from pump 17 will flow through channel 9, reversing valve casingH and channel 20 to the upper end of cylinder ti and cause piston 5 tomove die 3 downward into contact with the material in mold i, and theliquid expelled from the lower end of cylinder i by piston 5 will flowthrough channel i9, reversing valve casing Ill and channel 98 intoreservoir 8. 1

When die 3 engages the material in mold l, the resistance thereof willcause pump pressure to rise until it is high enough to raise valvemember M from its seat and then a part of the liquid discharged by pump1 will escape through low pressure relief valve 25, thereby limiting thepressure created by the pump' and consequently the force exerted by die3 upon the material in mold. l.

As soon as die 3 starts downward. motor 60 may be started by pressingone of the push buttons in control panel 38. Motor 60 will rotate shafts53 and 55 through the above described gearing at a very slow rate andthereby cause a screw 46 to be advanced and screw 49 to be redecreasethe resistance of high pressure relief I valve 26 until the resistancesof the two valves are approximately equal at which time the end of shaft55 will engage the actuating member of limit switch 68 and operate it tothereby cause motor 60 to be reversed and solenoid 31 to be energizedand shift selector valve 28 to the position shown in Fig. 2.

Shifting valve 28 to the position shown in Fig. 2 causes communicationbetween relief valve and channel 9 to be blocked so that pump 1! mustexhaust'its excess liquid through high pressure relief valve 26, andreversing motor 60 causes screws 46 and 43 to be rotated in a directionopposite to their former direction of rotation.

Screw 49 will gradually and uniformly increase the tension of spring 58,thereby causing a gradual and uniform increase in pump pressure with theresultant gradual and uniform increase in the force exerted by die 3upon the material in mold i, and screw :36 will simultaneously decreasethe tension of spring t5.

Screw M will continue to advance and increase the resistance of highpressure relief valve 26, and screw 46 will continue to retract anddecrease the resistance of low pressure relief valve 25 until theresistance of valve 26 has been increased to the predetermined maximumand the resistance of valve 25 has been decreased to the predeterminedminimum at which time the end of shaft 53 engages the actuating memberof limit switch 617 and operates it to thereby cause motor 60 to stopand solenoid 37 to be deenergized and permit spring 36 to shift valve 28to the position shown in Fig. 1, unless it is desired that die 3maintain the maximum pressing force upon the material in mold l for agiven period of time in which case solenoid 37 is not deenergized bylimit switch 57 but by a push button which is arranged in control panel38.

After the material in moldi has been compressed, reversing valve Iil isshifted to the position shown in Fig. 4 and liquid from pump 7 flowsthrough channel 9, valve casing H and channel it to the lower end ofcylinder t and causes piston 5 to raise die 3, the liquid expelled fromthe upper end of cylinder 6 by piston 5 flowing through channel 20,valve casing H and channels Ill and it into reservoir 8.

After die 3 has been raised the desired distance, valve I 0 is shiftedto the position shown in Fig. 1 and the several parts of the apparatusare in their initial positions and ready to start the second cycle ofoperation.

The invention herein set forth is succeptible of various modificationsand adaptations without departing from the scope thereof as hereafterclaimed.

The invention is hereby claimed as follows:

1. The combination, with a hydraulic motor, of a pump, fluid channelmeans connecting said pump to said motor, means for limiting thepressure created by said pump, said means being adjustable to vary pumppressure between a minimum'value and a maximum value and having by saidpower means for gradually adjusting one a pump, fluid channel meansconnecting saidpump to said motor, a low pressure relief valve and ahigh pressure relief valve connected to said channel means andalternately effective to limit the pressure created by said pump, eachof said valves being adjustable to vary its resistance between a minimumand a maximum and said valves being initially so adjusted that theresistance of one is minimum and the resistance of the other is maximum,means for gradually increasing the resistance of one and decreasing theresistance of the other of said relief valves to thereby cause one ofsaid valves to efiect a gradual variation in pump pressure from a firstto a second value and to simultaneously condition said other valve foroperation upon said second pressure valve being reached, andmeans forblocking communication between said low pressure relief valve and saidchannel means during the time the resistance of said low pressure reliefvalve is being decreased.

3. The combination, with a hydraulic motor, of a pump, fluid channelmeans connecting said pump to said motor, a low pressure relief valveand a high pressure relief valve connected to said channel means andalternately effective to limit the pressure therein, power means, meansdriven by said'power means for simultaneously increasing the resistanceof one and decreasing the resistance of the other of said relief valves,means operated by said driven means for reversing said power means, andmeans for blocking communication'between said low pressure relief valveand said channel means during the time the resistance of said lowpressure relief valve is being decreased. 7 l

4. The combination, with a hydraulic motor, of a pump, fluid channelmeans connecting said pump to said motor, a low pressure relief valveand a high pressure relief valve connected to said channel means tolimit the pressure therein, means for simultaneously increasing theresistance of one and decreasing the resistance of the other of saidrelief valves, and valve means operable in response to the resistance ofsaid high pressure valve being reduced to a predetermined minimum forautomatically blocking communication between said low pressure reliefvalve and said channel means.

5. The combination, with a hydraulic motor, of a pump, fluid channelmeans connecting said pump to said motor, a low pressure relief valveand a high pressure relief valve connected to said channel means -tolimit the pressure therein, Y

means for simultaneously increasing the resistance of one and decreasingthe resistance of the other of said relief valves, a selector valveconnectedbetween said low pressure relief valve and said channel means,yieldable means and electromagnetic means for shifting said selectorvalve into one or the other of two positions in the first of which itestablishes communication between said low pressure relief valve andsaid channel means and in the second of which it blocks communicationtherebetween, a switch'for controlling said electro-magnetic means, andmeans for operating said switch in response to the resistance of saidhigh pressure relief valve being reduced to a predetermined minimum tothereby cause said selector valve to be shifted to said second position.4

6. The combination, with a hydraulic motor, of a pump, fluid channelmeans connecting said pump to said motor, a low pressure relief valveand a high pressure relief valve connected to said channel means tolimit the pressure therein,

screw means for adjusting each of said relief valves to vary theresistance thereof, means for simultaneously rotating both of said screwmeans to cause one to advance and the other to retract and therebysimultaneously increase the resistance of one and decrease theresistance of the other of said relief valves, means for blockingcommunication between said low pressure relief valve and said channelmeans during the time the resistance of said low pressure relief valveis being decreased, and separate means for operating said blocking meansin response to eachof said screws reaching a predetermined point.

7. The combination, with a hydraulic motor, of a pump, fluid channelmeans connecting said pump to said motor, a low pressure relief valveand a high pressure relief valve connected to said channeltmeans tolimit the pressure therein, screw means for adjusting each of saidrelief valves to vary the resistance thereof, power means, means drivenby said power means for simultaneously rotating both of said screw meansto cause one to advance and the other to retract and therebysimultaneously increase the resistance of one and decrease theresistance of the other of said relief valves, means operated by saiddriven means for reversing said power means, and means responsive tooperation of said reversing means for blocking communication betweensaid low pressure relief valve and said channel means during the timethe resistance of said low pressure relief valve is being decreased.

8. The combination, with a hydraulic motor, of a pump, fluid channelmeans connecting said pump to said motor, a low pressure relief valveand a high pressure relief valve connected to said channel means tolimit the pressure therein, screw means for adjusting each of saidrelief valves to vary the resistance thereof, means for simultaneouslyrotating both of said screw means to cause one to advance and the otherto retract and thereby simultaneously increase the resistance of one anddecrease the resistance of the other of said relief valves, and meansoperable in response to the screw means for adjusting said high pressurerelief valve being retracted to a predetermined point for blockingcommunication between said low pressure relief valve and said channelmeans.

9. The combination, with a hydraulic motor, of a. pump, fluid channelmeans connecting said pump to said motor, a low pressure relief valveand a high pressure relief valve connected to said channel means tolimit the pressure therein, a first screw means for adjusting said highpressure relief valve, a second screw means for adjusting said lowpressure relief valve, a prime mover, means driven by said prime moverfor rotating both of said screw means simultaneously to cause one toadvance and.the other to retract and thereby increase the resistance ofone relief valve and decrease the resistance of the other relief valvesimultaneously, a selector valve for controlling communication betweensaid low pressure relief valve and said channel means, and meansresponsive to said first screw means being retracted to a given pointfor causing said prime mover to be reversed and simultaneously causingsaid selector valve to block communication between said low pressurerelief valve and said channel means.

iii/The combination, with a hydraulic motor, of a pump, fluid channelmeans connecting said pump to said motor, a low pressure relief valve 4and a high pressure relief valve connected to said channel means tolimit the pressure therein, a first screw means for adjusting said highpressure relief valve, a second screw means for adjusting said lowpressure relief valve, a prime mover, means driven by said prime moverfor rotating both of said screw means simultaneously to cause one toadvance and the other to retract 1 and .thereby increase the resistanceof one relief valve and decrease the resistanceof the other relief valvesimultaneously, a selector valve forchannel means, and means responsiveto said secnd screw means being retracted to a given pointfor stoppingsaid prime mover.

11. The combination, with a hydraulic motor, of a pump, fluid channelmeans connecting said pump to said motor, alow pressure relief valve anda high pressure relief valve connected to said channel means to limitthe pressure therein, a selector valve for controlling communicationbetween said low pressure relief valve and said channel means, a firstscrew means for adjusting said high pressure relief valve, a secondscrew means for adjusting said low pressure relief valve, the threads onone screw means being opposite hand to the threads on the other, adriven gear splined upon each of said screw -means, means forrestraining said gears from axial movement, a third gear meshing withboth of said driven gears, a prime mover for rotating said third gear tocausesaid driven gears to rotate said screw means and thereby cause themto move axially'in opposite directions and increase the resistance ofone relief valve and decrease the resistance of the other-relief valve,means for reversing said prime mover, and means for shifting saidselector valve to cause it to block communication between said lowpressure relief valve and said channel means during the time theresistance of said low pressure relief valve is being decreased.

12. The conrblnatiomwith a hydraulic motor, of a pump, fluid channelmeans connecting said pump to said motor, a low pressure relief valveand a high pressure relief valve connected to said channel means tolimit the pressure therein, a selector valve for controllingcomunication between said low pressure relief valve and said channelmeans, a first screw means for adjusting said high pressure reliefvalve,,a second screw means for adjusting said low pressure reliefvalve, the threads on one screw means being opposite hand to the threadson the other, a driven gear splined upon each of said screw means, meansfor restraining said gears from axial movement, a third gear meshingwith both of said driven gears, a prime mover for rotating said thirdgear to cause said driven gear to rotate said screw means and therebycause them to move axially in oppositedirections and increase theresistance of one relief valve and decrease the re- Z sistance of theother relief valve, means for reversing said prime mover, and means forshiftsaid selector valve to cause it to block communication between saidlow pressure relief valve and said channel means during the time theresistance of said low pressure relief valve is being decreased, saidreversing means and said valve shifting means being operable in responseto one of said screw means reaching a given point'in its axial movement.

13. The combination, with a hydraulic motor,

of a pump, fluid channel means connecting said pump to said motor, a lowpressure relief valve and a high pressure relief valve connected to saidchannel means to limit the pressure therein, a selector valve forcontrolling communication between said low pressure relief valve andsaid channel means, a first screw neans for adjusting said high pressurerelief valve, a second screw means for addusting said low pressurerelief valve, the threads on one screw means'being opposite hand to thethreads on the other, a driven gear splined upon each of said screwmeans, a means for restraining said gears from axial movement,a thirdgear meshing with both of said driven gears, a prime mover for rotatingsaid third gear to cause said driven gears to rotatesaid screw means andthereby cause them to move axially in opposite directions and increasethe resistance of one relief valve and decrease the resistance of theother relief valve, means for reversing said prime mover, means forshifting said selector valve to cause it to block communication'betweensaid low pressure relief valve and said channel means during the timethe resistance of said low pressure relief valve is being decreased,means responsive to one of said screw means reaching a given point inits travel for eflecting operation of said reversing means and saidvalve shifting means, and means for stopping said prime mover inresponse to the other of said screw means reaching a given point in itsaxial movement.

RANSOM TYLER.

